/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef LIBTEXTCLASSIFIER_UTILS_JAVA_SCOPED_GLOBAL_REF_H_
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#define LIBTEXTCLASSIFIER_UTILS_JAVA_SCOPED_GLOBAL_REF_H_
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#include <jni.h>
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#include <memory>
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#include <type_traits>
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#include "utils/base/logging.h"
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namespace libtextclassifier3 {
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// A deleter to be used with std::unique_ptr to delete JNI global references.
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class GlobalRefDeleter {
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public:
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GlobalRefDeleter() : jvm_(nullptr) {}
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// Style guide violating implicit constructor so that the GlobalRefDeleter
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// is implicitly constructed from the second argument to ScopedGlobalRef.
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GlobalRefDeleter(JavaVM* jvm) : jvm_(jvm) {} // NOLINT(runtime/explicit)
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GlobalRefDeleter(const GlobalRefDeleter& orig) = default;
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// Copy assignment to allow move semantics in ScopedGlobalRef.
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GlobalRefDeleter& operator=(const GlobalRefDeleter& rhs) {
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TC3_CHECK_EQ(jvm_, rhs.jvm_);
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return *this;
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}
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// The delete operator.
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void operator()(jobject object) const {
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JNIEnv* env;
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if (object != nullptr && jvm_ != nullptr &&
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JNI_OK ==
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jvm_->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_4)) {
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env->DeleteGlobalRef(object);
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}
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}
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private:
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// The jvm_ stashed to use for deletion.
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JavaVM* const jvm_;
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};
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// A smart pointer that deletes a JNI global reference when it goes out
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// of scope. Usage is:
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// ScopedGlobalRef<jobject> scoped_global(env->JniFunction(), jvm);
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template <typename T>
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using ScopedGlobalRef =
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std::unique_ptr<typename std::remove_pointer<T>::type, GlobalRefDeleter>;
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// A helper to create global references. Assumes the object has a local
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// reference, which it deletes.
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template <typename T>
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ScopedGlobalRef<T> MakeGlobalRef(T object, JNIEnv* env, JavaVM* jvm) {
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const jobject global_object = env->NewGlobalRef(object);
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env->DeleteLocalRef(object);
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return ScopedGlobalRef<T>(reinterpret_cast<T>(global_object), jvm);
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}
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} // namespace libtextclassifier3
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#endif // LIBTEXTCLASSIFIER_UTILS_JAVA_SCOPED_GLOBAL_REF_H_
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